THE SECRET SPIES IN THE SKY - Imagery, Data Analysis, and Discussions relating to Military Space

SatTrackCam Leiden (Cospar 4353) is a satellite tracking station located at Leiden, the Netherlands. The tracking focus is on classified objects - i.e. "spy satellites". With a camera, accurate positional measurements on satellites of interest are obtained in order to determine their orbits. Orbital behaviour is analysed.

About two hours later, US astrophotographer David Murr was watching the sky as part of an aurora watch in Louisa, Virginia. Just after he had set up, he saw and imaged a "cloudy blob" moving from SE to NW through Ursa major (just above the trees in the image):

After Murr's tweet and image were brough to my attention through a retweet by David Dickinson, I could quickly confirm this was related to the Sentinel-2A launch two hours earlier.

What is visible is probably fuel venting [but: see update below: it could actually be gasses from the actual last engine burn] by AVUM, the Attitude and Vernier Upper Module that assists in putting the payload into its intended orbit after separation from the third stage. The AVUM has liquid fuel engines (the Zefiro third stage has solid fuel engines) and did a final burn, aiming at de-orbiting it lowering its orbit, just 10 minutes before the observation (see timeline here).

The map above shows the predicted track for Murr's Virginia location for Sentinel-2A and the Sentinel Zefiro 3rd stage : it matches the sky track and direction of movement of the "fuzzy blob" on his image extremely well. There is a small time difference of only a few minutes, but all taken it is very clear this object was connected to the Sentinel-2A launch (the plot is based on orbital elements for the Vega 3rd stage and Sentinel-2A from some hours later: there are no orbital elements for the AVUM).

Murr was not the only one spotting and photographing the object: more photographs by several other US observers are here.

UPDATE 20:35 UT: Jim Cook from Germantown, Maryland, describes what appears to be the actual last burn of AVUM in a post on the Seesat list. Putting all information together, I have come to the conclusion that the fuzzy cloud is not so much a fuel vent, but gasses from the actual AVUM burn.Also: the press kit talks about a "de-orbit burn" for AVUM, but as AVUM has been catalogued as still in orbit (as in previous cases), it is a burn to lower the orbit rather than a true de-orbit burn.

(many thanks to David Murr for his permission to feature his photograph)

About the Author

Dutch, 47, PhD, stone age archaeologist, meteoriticist, satellite tracker, meteor observer, asteroid discoverer. Consultant in a Space Situational Awareness project with the Space Security Center of the Royal Dutch Air Force and Leiden Observatory. As an invited expert I advised members of Dutch Parliament about military satellite systems and their locations during a 2016 foreign affairs committee hearing about the MH17 disaster.
Asteroid (183294) Langbroek was named after me. In 2012, I received the Dr. J. van der Bilt Prize of the Royal Dutch Astronomy Association (KNVWS) for my work on meteors, asteroids and satellites.
Opinions expressed on this blog are entirely my own.
You can find me on Twitter via @Marco_Langbroek

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Excerpt from United Nations resolution 2222 (XXI)

Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies

In order to promote international co-operation in the peaceful exploration and use of outer space, States Parties to the Treaty conducting activities in outer space, including the moon and other celestial bodies, agree to inform the Secretary-General of the United Nations as well as the public and the international scientific community, to the greatest extent feasible and practicable, of the nature, conduct, locations and results of such activities. On receiving the said information, the Secretary-General of the United Nations should be prepared to disseminate it immediately and effectively.